Internal combustion engines are widely used for power, both domestically and in industry. For instance, internal combustion engines are commonly used to power vehicles, such as passenger cars, in the automotive industry.
The operation of an internal combustion engine can, however, be compromised by the presence of water in the fuel which is used in the engine.
Water may be present or introduced into the fuel at any point during its production. For instance, water may be present in the feedstock to the refinery in which the fuel may be prepared. Fuels, and particularly ethanol-containing fuels, are also hygroscopic which means that they may absorb water from the atmosphere, e.g. during transportation, in fuel storage tanks and even in the fuel tank of a vehicle.
Since water and fuel have different densities, then water may simply be removed from a fuel by withdrawal of the denser phase from the bottom of e.g. a tank. However, separation of water and fuel becomes more difficult when they mix to form an emulsion.
The presence of a water-fuel emulsion in an engine can have a number of unwanted consequences. For instance, the water can corrode metal parts in the engine, thereby increasing the frequency at which these parts need to be replaced. Water-fuel emulsions can also block fuel filters in the engine.
Demulsifiers are often added to fuels in order to break the emulsion. Once an emulsion is broken, water will sink and collect underneath the fuel from where it can be readily removed, e.g. in fuel storage tanks.
Common demulsifiers include those that are based on phenolic resins, esters, polyamines, sulfonates or alcohols which are grafted onto polyethylene or polypropylene glycols. These demulsifiers may be used in addition to other additives, which each carry out a specific function. It would desirable for an additive to be effective as an emulsifier, whilst also carrying out another function in the fuel.
There is a need for further methods for reducing the propensity of a fuel to form an emulsion, and for additives which may be used in fuels as demulsifiers.